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Purpose

An NHANES III dataset for analysis will typically include data from at least 2 data files. You will keep and merge data to include variables from different data files.

Task 1: Keep NHANES III Data

NHANES III data files are released by their collection method, and as supplemental data files. Many of these are very large data files with many variables. Most analysts will only need a few selected variables. You will likely wish to keep only those variables when you create your analytic dataset. This process is called keeping.

Task 2: Merge NHANES III Data

The basic data files were organized by their collection method, which can fall under one of four components: Examination, Laboratory, Adult or Youth Questionnaire, or Foods. To allow for timelier releases, supplemental data files (component updates and specialized sub-sections of these components) were released at later dates as they were completed. Joining the components of the data files is called merging.